Complexes of the Heavier Alkaline Earth Metals Ca, Sr, and Ba with O-Functionalized Phosphanide Ligands

Barium complexes with crown-ether-functionalised amidinate and iminoanilide ligands for the hydrophosphination of vinylarenes

Two barium-amide complexes bearing crown-ether-functionalised amidinate and iminoanilide ligands that act as competent precatalysts for the intermolecular hydrophosphination of vinylarenes are presented.

Synthesis, characterization and reactivity of potassium and barium complexes containing phosphane-borane stabilized methanides

The polymeric potassium complex [K{CH(PPh2BH3)2}]∞ (1) was prepared and used as a starting material for the syntheses of related N,N,N',N'-tetramethylethylenediamine (tmeda) and N,N,N',N',N''-pentamethyldiethylenetriamine (pmdta) ligated potassium derivatives [K{CH(PPh2BH3)2}(tmeda)2]∞ (2) and [K{CH(PPh2BH3)2}(pmdta)]2 (3). Salt metathesis reactions with [BaI2(thf)5] allowed the synthesis of the barium derivatives [BaI{CH(PPh2BH3)2}(thf)5] (5) and [Ba{CH(PPh2BH3)2}2(solv)2}] (solv = Et2O, thf) (6), which are more prone to subsequent reactions than the potassium derivatives. One of the resulting products, [Ba4O{CH(PPh2BH3)2}3{Ph2PCH(BH3)PPh2BH3}3] (7), which contains two different isomeric forms of the bis(borane) adduct of Ph2PCHPPh2, was isolated. The complexes were characterized by NMR techniques and single crystal X-ray diffraction measurements.

Alkaline Earth Metal Complexes of a Phosphine-Borane-Stabilized Carbanion: Synthesis, Structures, and Stabilities

The reaction between either MgI2 or CaI2 and 2 equiv of [(Me3Si)2{Me2(H3B)P}C]K (2) in toluene gives the corresponding organo-alkaline earth metal compounds [(Me3Si)2{Me2(H3B)P}C]2M in moderate to good yields [M = Mg (3), Ca (4)]. Compound 3 crystallizes solvent-free, whereas X-ray quality crystals of 4 could not be obtained in the absence of coordinating solvents; crystallization of 4 from cold methylcyclohexane/THF gives the solvate [(Me3Si)2{Me2(H3B)P}C]2Ca(THF)4 (4a). The corresponding heavier alkaline earth metal complexes [(Me3Si)2{Me2(H3B)P}C]2M(THF)5 [M = Sr (7), Ba (8)] are obtained from the reaction between MI2 and 2 equiv of 2 in THF, followed by recrystallization from cold methylcyclohexane/THF. Compound 3 degrades over a period of several weeks at room-temperature both in the solid state and in toluene solution to give the free phosphine-borane (Me3Si)2{Me2(H3B)P}CH (5) as the sole phosphorus-containing product. In addition, compounds 3, 4, and 4a react rapidly with THF in toluene solution, yielding 5 as the sole phosphorus-containing product; in contrast, compounds 7 and 8 are stable toward this solvent.